Grate or burner



v Jan. 14, 1947. F. P. D. scoT'r 2,414,397-

GRATE OR BU Filed Nov. 2, 1944 ATTOAIVE/S Patented Jan. 14, 1947 UNITEDSTATES PATEEQ GRATE R BURNER Francis Peto Dudley Scott, London, Engiand,as-

signor of one-half to Prior Stokers Limited,

London, England Application November 2, 1944, Serial No. 561,542

' In Great Britain November 9, 1943 1 Claim. 1

The duplex burner or grate of the present invention is of the kind inwhich fuel is fed to the bottom of and up into a. burner or grate withhollow walls or tuyres, provided with apertures near their upper marginthrough which combustion air is supplied, a single feed screw feedingboth parts of the burner, one upon each side of a hollow longitudinalmember. The feed screw terminates short of the end of the burner and adivision plate at the end of the feed screw separates the two parts ofthe burner beyond the end of the feed screw. The forward motion of thefuel in this part of the burner i commonly up a slope designed to avoidexcessive backward thrust on the feed screw and to maintain an evensupply of fuel to the combustion zone. Agitating or stirring means maybe incorporated at the end of the screw to help to keep the fuel moving.The hollow longitudinal member over the screw of the duplex burner isnaturally designed to present as little resistance as is practicablehaving regard to the desired movement of the fuel, but there is acertain tendency to packing under the end of the screw because of theupward slope with a consequent upward thrust. There is also sometendency to side thrust, particularly when stirring means are used, andthe fact that there is more resistance to the flow into the side of thelongitudinal member where it would normally be greater tends to increasethis. Moreover, with certain badly graded fuels there is found to be atendency to unequal grading on the two sides of the burner; when thefeeding worm is righthanded and therefore turning in a clockwisedirection viewed from the forward end of the burner the fines tend to gomore to the left-hand half and nuts more to the right-hand half of theburner as viewed from that end.

The present invention is designed to alleviate such conditions andincludes several parts or features which tend separately and incombination to do so. One part of the invention includes the extensionof the feed screw shaft under the longitudinal member into a forwardbearing and preferably the use of a reverse thread of relatively verysmall diameter on the shaft extension. Another part includes the use ofa feed screw located toward the side of the burner away from that wherethe fines would tend to predominate and an air duct led to the sideremote from the feed screw, so that the initial pressure of the air isavailable on that side where fuel bed resistance tends to be greater andthe arrangement is compact and economical of space. Other parts areembodied in a typical form shown upon the accompanying drawing. Theparts for which a monopoly is desired are those delimited by the claim.

In the drawing- Fig. 1 is a perspective view from the forward end,broken away to show the construction and arrangement of parts, and vFig. 2 is a diagrammatic view from the same end, making clear thepreferred location of the feed screw and air duct.

The feed screw l is arranged to feed fuel through the feed tube 2 to thebottom of a trough 'I and up into the burner. The trough is ofsubstantially \l shape in cross-section. The screw rotates clockwise asviewed and will consequently tend to feed a greater proportion of finesto the left-hand side 3 and of coarse to the right-hand side t of thetrough. The two sides of the trough are separated by a substantially Vshape longitudinal partition 5 which is curved down. at 6 to conformmore or less with the upward curve of the bottom and the tapering downof the main feeding thread of the screw I. A plenum space i is formedoutside the main casting 8 by brickwork 9 and supplies air over thelongitudinal partition 5 and into the tuyre castings Ill. Air issupplied to the plenum space by an air duct II. It will be noted thatthe feed screw is oifset from the centre of the apparatus toward theside 4 of the burner to which a, greater proportion of the coarse fueltends to be fed and that the air duct enters on the fines side i. Thefeed screw is extended into the forward bearing E2, the extension 33being provided with a reverse thread it between the main thread and thebearing, to agitate and help to raise the fuel at the forward end of thetrough.

In case fines get past the bearing length 15 of the extension a threadIt of the same hand as the main thread may be formed on a portion of theextension within the bearing to feed them out at the end or through anaperture provided for them.

I claim:

A duplex burner including the combination of a trough of substantially Vshape in cross-section with a rounded bottom, a substantially V shapelongitudinal hollow partition for the trough providing upwardlydiverging sides adapted to direct fuel upwardly, a tapered feed screwextending into the trough longitudinally thereof at the bottom to feedfuel upwardly to said sides, said partition being dependingly mounted soas to extend only partly into said trough and above the screw, means tosupply air to the trough and into the hollow of the partition, the screwcounteracting uneven burning of the fuel due to the resultant tendencyto feed fines to one side and coarse fuel to the other side by reason ofthe screw being offset nearer to the side of the trough towards whichthe upper side of the screw rotates and said air supply beingintensified on the side of the trough towards which the lower side ofthe screw rotates.

FRANCIS PETO DUDLEY SCOTT.

